Chinese whispers in Australia

We decided months ago that we would not comment on leaks of the draft of the upcoming IPCC report (due Feb 2007) but we are prepared to correct obvious errors. The ongoing revisions of the text and the numerous drafts make any such commentary, let alone conclusions drawn from it, pretty pointless. This is even more true when the leaks are obviously confused about a central point. The principle error in the latest ‘exclusive’ is that the writer confuses a tightening of the estimate of climate sensitivity to 2xCO2 (as discussed here) with projections of climate change in 2100. These projections obviously depend on the uncertainties in the scenarios of future technology, economic progress and population (etc.) plus uncertainties in feedbacks related to the carbon or methane cycles. Unfortunately these have not been reduced since the last assessment report (and in some cases have actually increased).

That occasional stories will come out that get basic things wrong is unfortunate but not surprising. What is more troubling is that they subsequently get picked up by Reuters and UPI, and republished in places (such as Scientific American, though in their defence, it is simply a posting of the wire report) where the editors should know better. Worse still, the wire service stories are too brief to make the source of the error obvious, and thus the error gets propagated in an ever more confused state. As usual the blogsphere is playing a key role in amplifying and further muddying the story. The advantage of blogs is that errors can be corrected quickly, and the comments on Prometheus for instance, quickly revealed the confusion and the potential agenda of the original story.

There will be plenty of time to discuss the new IPCC report when it comes out and where everyone can read for themselves what has and what hasn’t changed since 2001. Until then, we would counsel against journalists and editors jumping at supposed ‘exclusives’ and – more dangerously – going ahead with them without even a basic sanity check of the details.

Working group 1 of the IPCC received comments in the latest round, that because of errors such as this systemic bias in all the AR4 models, that all predictions and projections based on these models is premature. The Roesch study is especially significant, because in addition to the average errors being larger in effect than the total estimated increase in forcing since 1850, all the globally averaged albedo biases are in the positive direction, i.e., against solar forcing, the leading competitive theory to the relative significance of the anthropogenic greenhouse gasses for recent warming.

[Response: You’ve been shown over and again (and again and again) that this is incorrect reasoning. Repeating it will not suddenly make it right. – gavin]

This shared systematic bias undermines the IPCC TAR argument that the models are independent enough that combining the models into ensembles will cancel their errors, and make their combined results more trustworthy.

Furthermore, the usage of models in other “observational” assessments of climate sensitivity to CO2 also render those results suspect.

If the IPCC report is truly subject to peer review, this draft will have to be considerably revised. In fact, so much of the modeling science is now in question, that the IPCC report should be delayed a couple of years, so that the modelers have a chance to implement their corrections.

[Response: IPCC is not a stamp of aprpoval. It is an assessment of the state of the science. To put it off until things were perfect is the same as never doing it. IPCC’s role is to fairly assess what is well understood, what is less so, and what conclusions, can or can’t be drawn at the moment. There are multiple levels of uncertainty in many aspects of climate research (though the one you keep harping on is not the most interesting or important), but IPCC is there to highlight the nuggets that are reasonably known. -gavin]

i disagree with your take on blogs, “As usual the blogsphere is playing a key role in amplifying and further muddying the story.” after all, blogs are not taken sooo seriously are they? and where is the fault in ‘amplifying’ – i take this in the sense of getting a message to more people, as well, even when people get it wrong on their blogs there is then at least a possibility that they may be corrected or otherwise moved to re-examine their thoughts, better on blogs than under rocks eh?

that said, this blog (it is a blog isn’t it?) always gives me hope, i am not a scientist but your careful, geometric, (even sometimes niggling), approach has my admiration and support

Gavin, I did not realize that you thought you had made your case. Your comment that

“You need to appreicate that these changes in the fluxes are really small compared to the absolute flux, on the order of a few percent at most – thus they don’t generally change the big picture climate in the models and I have seen no evidence that there is a systematic relationship to the sensitivity.”

is strange from a modeler and author that claims to have modeled the energy imbalance of the earth to 0.85+/-0.15 W/m^2. That is why I couldn’t take your “few percent” dismissal of the results without more substantiation. When you admitted that you used the GISS-ER model instead of using the GISS-EH model, I assumed you knew that Roesch had reported that it had a larger globally averaged annual surface albedo errors than the GISS-EH model.

A surface albedo error of just 1% when applied to the globally averaged annual surface solar flux over 160W/m^2 is over 1.6W/m^2. Note that this is at the surface and not TOA.

The errors in the GISS-ER model probably explain a significant portion of the deviation from 1 of the 0.92 effective forcing that you and Hansen used for solar forcing in your “…Energy Imbalance…” paper, i.e., by using “effective” forcing you apply this model error twice.

I don’t need to have things explained to me over and over and over again, just once if it makes sense. Far from being convinced, I was expecting retractions of those papers or whatever the climate modeling equivilent of retraction is. How can you justify claiming a 0.92 effectiveness for solar forcing and a matching of the earths energy imbalance to 0.85+/-0.15W/m^2, in a model with errors larger than that, especially when those errors are a specifically against solar forcing? I admit that the models and forcing data have other errors probably much larger than that, but I don’t see how that helps your argument.

[Response: I did explain it, and for the sake of passer-by’s I’ll explain again – but that’s it. The 0.85 W/m2 imbalance is the difference between a perturbed run (i.e. with anthroipogenic forcings) from a balanced control run (without any forcings). There is no uncertainty in that number other than the interannual variations in the radiative balance over individual simulations (and that is the basis of the error estimate). Now you point out that the absolute value of the absorbed solar is off by some value x W/m2. Since the control run is balanced, the other component (outgoing LW) must also be off by the same amount. In the perturbed runs there is a reduction in LW out due principally to the GHGs (roughly 1.6 W/m2 by 2000) which is only partially cancelled by an increase in temperatures (causing increased emission of about 0.8 W/m2). Neither of these two perturbations have anything to do with x – the absolute error. I gave you, as did Isaac Held, exactly analogous examples of why your comparison of absolute error x with the net difference 0.85 is erroneous. Similarly, the ‘efficacy’ of solar forcing has nothing to do with the albedo errors – the efficacy is defined with respect to the forcing at the tropopause (which has already factored in the albedo issue). Instead it is a function of the latitude and height distribution of solar forcing compared to CO2. Regardless, 0.92 efficacy makes no practical difference to our attribution of changes to solar forcing because long term solar is not known to better than 10%. There is much to criticise about climate models – I do it myself all the time, but you need to understand what is being done. Instead of just reading Roesch’s interesting paper, I suggest you read the modeling papers you purport to be criticsing. Then come back. – gavin]

[Response: Martin, a more simple analogy I use for this: I can measure the height of my desk above the floor down to an accuracy of a few millimeters. This difference measurement is not called into question if someone tells me that the absolute height of my floor above sea level is only known with an error of +- 5 meters. -Stefan]

I read the two papers we are discussing particularly closely as well as many others. The solar effectiveness is derived from short model runs (10 years?) with the ocean held constant. Keep in mind that the surface albedo errors, specifically impact both the lattitude and height distribution of the solar forcing compared to CO2. The GISS-ER globally-annually averaged surface albedo is approximately 0.131 compared to satellite observation values of 0.121 and 0.124. While these averaged values approximately correspond to errors of 1.6 and 1.1W/m^2 reletive to the respective observations, the actual errors are locally much larger. The actual errors are concentrated at the tropical deserts and at the temperate snow cover in spring. I doubt correcting TOA albedo via cloud parameters is equivilent in both its latitude and height effects.

The fact that you can match an energy imbalance by perturbation with anthropogenic forcings alone, doesn’t mean that it also couldn’t be done with a correct solar, especially since the correct solar isn’t known with the needed level of accuracy. Unfortunately if you want to attribute a watt/m^2 of energy imbalance to different candidate net forcing increases, the models will probably need to be accurate to 0.1W/m^2 to do it with any resolution. With solar activity being at one of its highest levels in 8000 years per Solanki, attributing the recent warming in the context rapidly increased GHGs is problematic. We probably only have a couple decades of data accurate enough to validate the models to the required level of accuracy, and we probably need much more data.

[Response: You might want to read them a little more carefully then. The model estimates are from coupled runs 120 years long, and the means are estimated from a 40 year mean. You appear to be under the impression that the imbalances are calculated by compariing the absolute fluxes at TOA with the modelled fluxes. They are not. They are calculated by looking at the difference in the modelled fluxes only. Thus the observational uncertainty/model bias doesn’t come into it except indirectly. – gavin]

I was referring to the runs from which the 0.92 solar effectiveness is derived. I quote: “We include results for 10-year runs in our tabulated comparisons below.”, and I beleive those runs for the effective solar forcing are done with fixed Sea Surface Temperatures, not coupled runs. See “Efficacy of climate forcings”.

I occurs to me that such runs emphasize the differences and thus the errors between the forcings. The surface albedo errors when averaged over just land are much larger, since that is where Roesch found the errors. The match over the oceans was generally good.

[Response: That’s only for the Fs* calculations because they assume fixed SST and so don’t need to be run longer. The efficacies you are talking about are Ei and Ea which are calculated using the coupled model runs. -gavin]

I am continually disappointed at the level of inaccuracy in media reporting of AGW issues. I’ve given up expecting journalists to know the difference between T(2xCO2) and net warming by 2100, or any number of similar (very basic) things. But I suppose I shouldn’t be disappointed; I should realize that this is the way of the world. The question arises, can we do anything to change the state of affairs?

Perhaps. The moderators of RealClimate might prepare a document about the *basics* of AGW, some of the most common misconceptions and points of confusion, and basic definitions of things, specifically for journalists. This should not be an essay, but as brief as possible — just a few pages at most. Then they’d at least have no excuse for lacking the appropriate background to approach the topic more accurately.

I’m tempted to do so myself — but as a mathematician (not a climate scientist) it’d be another case of someone stepping out of his field. Lord knows I’ve heard enough naivete from legislators, attorneys, and sociologists — even from Steven Hawking! Perhaps this could be a group effort, by the readers of RealClimate, with the final form requiring the endorsement of the RealClimate mods, and sent to journalists under their auspices — lending both accuracy and credibility to the final result.

If we can induce even one journalist to “get things right,” then it might be worth it. Opinions?

You appear correct regarding the 100 year vs 10 year, although it appears to not make any difference, because per the definition of Fe in table 1 of “Efficacy…”

Fe = EaFa = EsFs

And table 3 where the Solar figures and Fe are derived from bears out the equation/definition, since both calcuations give an Fe of 1.10. I find that you are also correct regarding the use of coupled models, at least for the EaFa version. I apologize. I must have been confused by the large amount of fixed SST calcuations that were discussed, and the fact that somehow an “a priori fixed SST forcing, Fs” value can match a coupled model calculation so well.

None of this supports the idea that calculating Fe with a model with these positive surface albedo errors is valid or eliminates the anti-solar bias, especially given the latitude and height dependency of the figures.

I will review other sites where I have discussed your work, and make corrections, if I have incorrectly portrayed these calcuations.

The paper that originally propogated the misinformation in this case is a Murdoch-owned Australian daily which frequently takes a climate skeptical editorial line. It seems to me they just seized on some numbers in the IPCC draft which they could spin to support their usual viewpoint. I guess “IPCC narrows climate sensitivity error bars” doesn’t have quite the same appeal as a headline.

The guilelessness of some of our hosts on this blog is both endearing and frustrating at times. It’s possible that this example is an accident, but the tactic of planting false or misleading information in an obscure newspaper in order to have it picked up by the wire services and published as fact in major newspapers is a standard operating procedure of those who wish to impede progress (on global warming as well as other issues). Vicious personal attacks on the bearers of bad news (e.g., Jim Hansen) is another SOP. I’m afraid Hanlon’s razor is not a useful rule in these times.

I’m not a climatologist (a retired biologist with a math phobia) but have been following realclimate for about 6 months (ever since I read Flannerys book). Much of it I don’t understand but the above article sent me back to the original article on CO2 sensitivity which I reread along with the very long discussion.

Here is my naive take on all this (I hope I’m wrong). The calculation of 2XCO2 sensitivity by 2100 does not take into account any of the positive feedbacks to warming which we are already seeing and which are very large compared to the negative feedbacks. So the estimate of around 3 degrees C has little to do with what one really can expect i.e. we really expect much higher increases and much sooner. If that’s the case, the situation looks very bleak indeed and I might as well give up my efforts at conservation and efficiency and spreading the message???

[Response: You are not alone in being confused! The first thing is to separate out the sensitivity to 2xCO2 from what will end up happening in the real world. The 2xCO2 number is not tied to any particular year and (as you correctly point out) doesn’t include a number of potentially important feedbacks on the carbon cycle (because if it did, you’d have more than 2xCO2!). This number is also something you can realtively easily calculate from models or from (some) observations. Now the second number – what will temperatures be like in 2100 is a different thing entirely. This depends not only on how sensitive the climate is, but on what we end up doing to push the climate around. We might not reach 2xCO2 at all, or we could exceed it. Carbon cycle feedbacks may be small, or large. Thus there is a lot more uncertainty in the 2100 temperature. It is important as well to note that while you personally cannot do anything about how sensitive the climate is (that is purely a function of the physical system), you (along with the rest of us) are able to affect the trajectory of greenhouse gas growth and thus affect temperatures in 2100 (and before of course!). There is nothing in the IPCC report that should give you cause to think that there is no hope left to avoid the worst consequences of climate change. – gavin]

This applies to # 343 as well:
A journalist is a person who knows nothing about it, but he is the public’s messenger. [The people at scientific publications are exempt from this category because they are publishing exactly what scientists write.] I found this out in the early 1960s when I was still in high school. The story in the newspaper had nothing to do with the real event. What it sounds like is more important than what it is. Since then, this has been confirmed many times. Sensationalism [Yellow Journalism] sells subscriptions. Broadcast news programs are classified as entertainment because that is what they are. It won’t get better until a high school diploma includes a B.S. degree in science. Until then, it would be nice if EVERY news story about science were required by law to be edited by the scientist, not just the early publications. Of course, this runs afowl the First Ammendment to the US Constitution. You are between a rock and a hard place or between the “devil” and the deep blue sea. Anything you say will be not just MIS-interpreted thruough profound ignorance but eventually DIS-interpreted by willful propagandists and by people who just want to make you angry. You have to consider insanity, stupidity, ignorance and a third grade level of reading comprehension to be “normal” because they are. The only solution I have is to “wait 4 million years for further evolution to produce a creature worthy of the name Homo Sapiens”. [Yes I know that evolution doesn’t have a direction like that.] I mean: as far as a solution to the problem goes, I give up, but the problem is bigger than you thought. You were lucky that the journalists got the subject right and you should praise them for that.

Errors such as these are peppered through the press. I recently came across an article in Australia’s Business Review Weekly (BRW), which stated that, under an emissions trading scheme, electricity prices will rise by 300%. Underneath the text was a graph that clearly showed a peak increase of around 15%.

It’s so frustrating, because this type of misinformation can have a big impact on the sentiment of the population, which influences political legislation, and the general public is particularly susceptible to anything that will hit the hip pocket. Nobody would have bothered to look more closely at the graph, I only did it because I am involved with emissions reduction technology and intuitively I knew that the number was wrong.

I think that everyone needs to be on their toes to correct and inform those that are making the (let’s assume) error. While the damage has been done in the initial print run, the combination of a correction in the next edition plus a sense that people are watching can’t hurt. Maybe it won’t solve the problem, but what else can be done?

Gavin, with regards to “Reporting on Climate Change: Understanding the Science” from your reply to #7, since you linked to it, I decided to read through it a bit to see if it covers some “basics” I might have missed. In chapter 1 on page 2 it says:

Climate change, during the whole human past, has forced fundamental changes in how people live. It has influenced the beginnings and ends of cultures and civilizations. Global cooling – what we know as “ice ages” – has occurred as regularly as global warming, bringing large-scale benefit and harm to humans and other species. During the mid-1970s, many leading climate scientists were warning of the onset of another ice age and urging the government to take action to avert disaster.

I also wasn’t particularly impressed with how some of the “facts and myths” questions were written or answered. For now, I’m going to carry on reading…

[Response: Point taken. I have interacted with Bud Ward on a number of occasions and he is very open to improvements that can be made to the materials. Feel free to email him with any suggestions. -gavin]

Dear Group, nice to see you are still not commenting on comments on the IPCC. Just a friendly : I told you so.

The Economist looks like a must buy this Friday for its special on Climate Change. Given that, and to its disgrace and only last year, it was almost a sceptic and denier it will be interesting to see what its position is today. We should all be able to guage better the accessibility of Climate Science to the rich and powerful and to the intelligent reader and voter.

I agree that Roesch’s results are not that important or interesting as far as climate research. It is not a new discovery that snow is highly reflective, nor is it a surprise that a forest and other vegetation in a snow cover area casts shadows on the snow that significantly alters albedo, adding complexity to models.

However, as far as climate modeling (not the climate itself), Roesch’s work is perhaps the most important of the IPCC diagnostic subprojects, because of two results.

ALL OF THE AR4 models had a systematic POSITIVE albedo bias, so they are less independent than has been assumed and the practice of summing or averaging the results in the hope of cancelling errors or reducing noise is plainly shown to be based on false assumptions.

Second, Roesch’s work shows that regional albedo errors are large in their impact on the global energy budget, and therefore we cannot just accept modeler and IPCC handwaving about how the models differ in their regional distributions of temperature and precipitation. They must do much better in certain regions such as the temperate snow cover areas in both the total amount of cover, the type of vegation, the snow water equivilent (so that they get the timing of the spring melt right), because the effects on the albedo and energy budget are highly non-linear and the errors are larger than the energy imbalances that have caused the recent warming.

Unfortunately, the models also have significant positive albedo errors in the tropical deserts, and Roesch did not provide much insight into what the models might be geting wrong there. In terms of the climate and not the modeling, I find this the most curious part of the his results, because it still seems unexplained. One would think that they would be a simpler part of the surface and the observations and thus easier for the modelers to get right. Perhaps dust and aerosols are the confounders.

As far as putting off the IPCC report, I agree it is useful to have an assessment of the state of the science, if it is objective. However, the authors are climate scientists and those that are not modelers are probably still highly dependent on models for components of their research. It is simple human nature for them to want to cling to several years of work and not throw it out based on the obvious implications of the Roesch results. The errors are systematic and larger than what we are trying to measure and project and cannot be papered over by summing and averaging. All the global attribution and prediction work must be thrown out and redone, and much of the other work must be dismissed quantitatively and just mined for possible qualitative insights. It will be much easier on the authors human natures and less stressful on their scientific integrity, if we just postpone the next report a couple years.

[Response: This is my final comment on this. The fact that averaging of different model results demonstrably increases the skill when compared to any individual model is possibly surprising, given that there are systematic biases in the models, but this is not an assumption, it is a result. The conclusion from this result (which was true for the original CMIP, CMIP2 and for the IPCC AR4 models) is that much of the error in climate models is not a systematic bias, but is uncorrelated across different models and thus can be minimised through averaging. Arguing that all models and the successful matches they have to many kinds of variability should be tossed out because of a 1.6 W/m2 error in surface fluxes is frankly ridiculous. – gavin]

The average positive albedo bias of the AR4 models as reported by Roesch (0.016 to 0.019) corresponds to 2.6-3.1 W/m^2. The GISS-ER model was a little better than average. You are right, the uncorrelelated errors must dwarf this and other correlated errors. I am not arguing that the matches to various climate behavior are not a significant achievement and a validation of some of the basic physics within the models, they are. What should be thrown out are the quantative attribution of recent warming and the quantitative projections. The models just aren’t accurate enough to model and attribute under 1 W/m^2 global energy imbalances. I do believe that there is sufficient evidence to consider anthropogenic greenhouse gasses a significant contributer to recent climate warming on the principles of physics alone, but whether its contribution is 15% or 70% vis-a-vis solar, is just not within the skill of the models. The fact that they have been tuned to match variability against a period of warming, while have systematic biases against solar only decreases their credibility and calls into question their 2*CO2 sensitivities, because that is probably where some of the compensating errors landed.

I consider the models, warts and all, to be remarkable achievements, and well worth further investment, but we don’t have the data and understanding yet to produce and validate the models to the approx 0.1W/m^2 globally and annually averaged, needed for useful attribution and projection.

Re#14 Individual scientific integrity is not as important as the effects on human society of climate change induced freak weather. Fortunately climate scientists realise this. Bearing in mind the precept that science builds upon former endeavour, to put off the report would be to stem the flow of knowledge.

Re#17 So, if we do discover, absolutely and without any uncertainty, that the sun is responsible for 50% of the warming, what can we do about the sun? If we suspect that anthropogenic CO2 is responsible for, say, 30%, could we do anything about that? Do you see my point?

If we find that the sun is responsible for 50%, then we continue to study the Sun. Solanki (Nature) noted that based on past periods of high activity in the paleo record that there is less than 8% likelyhood of the current high levels of solar activity lasting another 50 years. Proponents of the solar conveyor theory predict that the next solar cycle will be particularly active, but that the current slowing of the conveyor means that the following cycle will be much less active.

If CO2 is responsible for say 30%, we do what the market signals are telling us anyway, become more energy efficient. But given the uncertainty, there is no reason to sacrifice hundreds of billions of dollars of economic growth. The wealthy can afford the luxury of long range environmental thinking and research and have the power and resources to “weather” extremes and develop the technology which may reduce our environmental footprint. I use compact flourescent lights (and am eagerly waiting for LEDs to become economic), and my next roof will be white, these are good strategies no matter what the cause of recent warming.

My point is, there is not yet good enough evidence to justify uneconomic expendatures and fearmongering about global warming. Curing diseases or discovering and diverting near earth asteriods may be more beneficial to humanity, so maximizing world economic growth is the best strategy to prepare for future known and unknown risks.

RE: #19 – What happens to California over the next 20 years will be an interesting experiment, to say the least. The first time a major political entity took this sort of risk based solely on the results of still-being-refined models. Here is the perspective. Arnie guesses that enough other political entities will do the same, that we will not lose our industry. He also guesses that the PR value of “being green in California” will retain businesses and even feed new technological spend (e.g. solar cells, etc.) Quite a risk when there are much more business friendly states out there (e.g. they are already demonstrably more capitalistic then this quasi Scandanavian state) who would be superior places for developing and manufacturing “green” technology. Heck, why not do it in the PRC, for that matter? So, we’ll be both capped and tapped.

I’m sure this is getting well off-topic but, while conventional energy prices are rising, don’t you think that economic growth is being somewhat restricted to the providers? Less expensive, renewable energy is going to maximise world economic growth. Without fouling the air and water, and without promoting more catastrophic and expensive weather events. Climate events and disease restrict economic growth.

My hope for the next IPCC report is that the specific criticisms in the recent NAS report are addressed specifically. What a wonderful opportunity for the IPCC core contributors to admit where they have been in error, to defend where they are right (by this I mean, objectively right, not “legend in your own mind” right) and to set out a course for a more refined and in depth understanding of climate change, and all the factors driving it, anthropogenic and non anthropogenic. In the realm of anthropogenic factors, I think it’s time for the IPCC to address things beyond GHGs while of course continuing to improve our understanding of GHG related mechanisms and impacts. In the real of non anthropogenic factors, I thing a much more interdisciplinary approach is needed, bringing in more astrophysicists, experts in incident cosmic radiation, experts in plasma physics, and from another perspective, a much greater contribution from classical Earth Sciences. From the statistics front, there is wealth of experience and knowledge to be tapped outside of the traditional confines of “Climate Science.” A motto of a famous university “Let There Be Light!”

[Response: Thanks. I don’t think we’d have thought of that …. – gavin]

My hope for the next IPCC report is …
[Response: Thanks. I don’t think we’d have thought of that …. – gavin]

I’d say the question behind #22 is whether, as an institution, the IPCC is intrinsically capable of adopting a broader church approach. AR4 may tell us.

[Response: Also re 22: I think it is more realistic to view IPCC as a process which temporarily brings together a large group of scientists to do a particular job, rather than as an institution. I am co-authoring a chapter in the upcoming IPCC report (and it happens to be the chapter dealing with the topic of the NAS report). There is no “institution” telling us what to write – we simply make our best effort at writing what we think is a correct assessment of the existing scientific literature, and we’ve put out our efforts for criticism by the wider community in three rounds of review now. We don’t think of the last IPCC report in terms of “we were wrong or right back then”, or needing to defend anything, because none of us was an author of the last report. It’s simply a new group of people looking at the evidence with a fresh mind. -stefan]

“We don’t think of the last IPCC report in terms of “we were wrong or right back then”, or needing to defend anything, because none of us was an author of the last report.”

If that is the case, shouldn’t more care or clarifying information be provided when using phrases such as “more…confidence”, “higher…confidence”, “increasing…confidence” and “greater…confidence”, since the natural implication is that this refers to that perhaps unjustifiably high confidence expressed by the authors of the TAR?

Any “high…confidence” in models’ skill to reproduce the paleo climate, should be quantified, so that it is clear what level of skill was required for such relatively coarse reproductions of paleo climate behavior modes, and that these comments should not be viewed as supportive of the skill levels needed to attribute the recent warming or to project the next century or so of future climate. The meaning of expressions such as “high…confidence” should be standardized or explicitly qualified so that it is clear that their meaning does not spill across the various chapters.

Dear climate thinkers, Given the current lack of regualiton of Greenhouse gas emissions, I assume there is a theory that claims that our increasing of greenhouse gases are not contributing to global warming? If so, can anyone direct me to the location of a credible resource showing a head to head comparison of the weight (and type) of evidence for the effect of GHG versus the weight of evidence for the claim that GHG is not contributing to global warming?

That is, evidence that supports the Greenhouse Gas Effect theory Vs evidence that support the counter theory that increasing greenhouse gases are not contributing to global warming.

[Response: Curious logic…. But the best assessment of all the possible theories is the IPCC report (see the links on the right). – gavin]

Are you sure that the phrase: “1.4C and 5.8C on current levels by 2100, but better science has led them to adjust this to a narrower band of between 2C and 4.5C.” Doesn’t refer to the improvements in the sensitivity over the whole range of emissions scenarios?

[Response: 2 to 4.5 C refers to sensitivity to 2xCO2 – but is applicable to the whole range of forcings. 1.4 to 5.8C is the range of temperature at 2100 over all the different scenarios – they are related but they are not the same. Most of the range at 2100 is related to the range of scenarios, not the range in sensitivity. -gavin]

Man, this story really brought out the anti-climate science lurkers! I guess that most of them only bother talking when the story is an IPCC one – maybe that’s the only one that they’re really worried about, since a strong IPCC could actually lead to policy outcomes. I mean, every other story on RealClimate gets maybe zero to two “”skeptical”” posts, but this one has several, and not just from Mr. Lewitt. The Prometheus link you cited, http://sciencepolicy.colorado.edu/prometheus/archives/climate_change/0009161_degree.html , has a bees’ nest of lurkers, many of them more misinformed than here. The sociology of this story is fascinating, as much of the native-English world is waking up to the reality of fossil-fuel-caused climate change. Most of the rest of the world is there already, of course.

One tiny correction, gavin, in your response to Mr. Lewitt’s increasingly voluminous posts #14, you said that “The conclusion from this result… is that much of the error in climate models is not a systematic bias, but is uncorrelated across different models and thus can be minimised through averaging” The bias in each model may be systematic, or it may not. However, the fact that the error is uncorrelated means that averaging will improve the result. This is often done in measurement generally – if I measure a given length with 3 rulers from different manufacturers, and take the average of the 3 lengths, I will get a more precise result if the rulers’ errors are uncorrelated. Manufacturer A may always be high, and B may always be low – hence systematic errors – but the average is more precise because of this. This is silly for rulers, but not so silly for femtogram masses or pooled astrophysical measurements. Anyway, you’re still almost assuredly right – the biases aren’t systematic, but they *could* be, and averaging would still be a good trick. By the way this “average of independent models” is called bagging in the machine learning literature, and it’s been working there since Leo Breiman suggested it in 1996. See http://en.wikipedia.org/wiki/Bootstrap_Aggregating for examples.

[Response: Thanks. You are correct of course. I was referring to systematic biases across models (which do nevertheless exist), as opposed to systematics biases within each model (which certainly exist and can be very significant). In climate circles, this averaging is generally referred to as a ‘meta-ensemble’ but thanks for the link to the other fields’ usage. -gavin]

With respect to comment #3 and the two responses to it, we might try another tack. With respect to total error of the model, a 1 W/m^2 absolute error is about 1% of the total – which is not bad, actually, 99% correct. An example of another measurement with significant global error but only modest relative error is mass of the Earth. We know the absolute mass of the planet in kilograms to the precision of Newton’s constant G, which in 2006 has a 95% chance of being accurate to 0.030% ( http://physics.nist.gov/cgi-bin/cuu/Value?bg|search_for=G ). Before 1998, discrepencies in reported values led to an absolute error 100 times this, namely 3% ( http://www.nist.gov/public_affairs/update/upd000508.htm#Weights ). Clearly before 1998, we could measure things to relative precisions of better than 3%! In fact, the gravitational attraction power of the Earth, GM, has been known to about 1 part per billion = 0.0000001% since 1996 from bouncing lasers off the LAGEOS satellites ( http://cddis.nasa.gov/lw13/docs/papers/sci_dunn_1m.pdf ). I really fail to see how this absolute error in the models matters, save as a linguistic tool to cast doubt on unfavourable results.

Re #32 where Steffen wrote “the fact that the error is uncorrelated means that averaging will improve the result.”

There are two mistakes being made here. First we do not know if there is a systematic error, because the models cannot be tested against the future climate they are predicting. Second, if a systematic error does exists it will not be uncorrelated because all the models share the same algorithms, which are published in the literature. In other words it is a double whammy!

The wealthy can afford the luxury of long range environmental thinking

That presumes that the consequences of environmental change are slight and absorbable. Some scenarios are horrific for all and produce economic conditions that would make wealth evaporate like snow in the sun.

Global warming gases trapped in the soil are bubbling out of the thawing permafrost in amounts far higher than previously thought and may trigger what researchers warn is a climate time bomb.

“The effects can be huge,” said lead author Katey Walter of the University of Alaska at Fairbanks said. “It’s coming out a lot and there’s a lot more to come out […] I don’t think it can be easily stopped; we’d really have to have major cooling for it to stop.”

Scientists worry about a global warming vicious cycle that was not part of their already gloomy climate forecast: Warming already under way thaws permafrost, soil that has been continuously frozen for thousands of years. Thawed permafrost releases methane and carbon dioxide. Those gases reach the atmosphere and help trap heat on Earth in the greenhouse effect. The trapped heat thaws more permafrost and so on.

I wish I could. But — unfortunately — it just might be as bad as it sounds. It might be even worse.

*As far as I know*, climate models include as many factors as practical but do *not* include feedbacks to the GHG cycle. In particular, they don’t treat the increase in GHGs, esp. methane, that may result from global warming. Frankly, the model forecasts are plenty scary without such feedbacks, but *with* them (and their reality is hard to deny) things are, as you say, far scarier.

Be afraid. Be vary afraid. And vote the bums who are obstructing action on this issue, the hell out of office.

Well, even if the actual state of affairs is that climate warms by, say, 4.5 degrees C by 2100 (the new upper sensitivity of 2Xco2), or even 3 degrees, (1) that’s pretty dangerous; and (2) it says nothing about how hot it will be in 2150 or 2200. So, we’re certainly not in the clear.

As much as we might debate the pros and cons of Steve Irwin’s career, I don’t think Crocodile Hunter (#40) has a right to his legacy. Barley at high latitudes as a trade-off for disruption of low- and mid-latitude agriculture that sustains billions? Crikey!

Re #39 It is not as bad as it sounds because in an atmosphere as rich in oxygen as that here on earth, methane has a very short lifetime of 8.4 years. http://en.wikipedia.org/wiki/Methane#Removal_processes Moreover, the amount of methane being emitted as the permafrost melts, 3.8 Tg per year, is small compared to the estimate of total global methane production, which is 600 Tg per year. Finally, there is a fixed amount of methane in the Arctic, so once it has been released and oxidised it is no longer a threat.

That is the good news – now for the bad news :-(

There is another melt going on in the Arctic, and that is the Arctic sea ice. As it melts, it is releasing the main greenhouse gas – water vapour. Of course H2O has an even shorter atmospheric lifetime than methane, but the quantities that will be added to the atmosphere will far outweigh the effects of methane. Moreover unlike methane which is destroyed, there is effectively an unlimited amount of water available since it is recycled.

The reason that the scientists are panicking about methane is because they fear it may have been the cause of the unexplained rapid warming of 20K at the end of the Younger Dryas (YD) stadial. However, recent tests of the Greenland ice cores at the YD/Holocene boundary have shown that there was no sudden increase in methane then. The YD rapid warming was most likely caused by the increase in water vapour when the sea ice that stretched as far south as Ireland suddenly disappeared.

Personally, I’m not particularly impressed with what I’ve seen so far. Dealing with AGW is treated like getting insurance – chuck a bit of money in, and maybe things won’t be so bad. When I get a chance I’ll try to read the whole (or most of) the article. I’m not sure if I’ll learn anything new.

I feel that one of the biggest issues with actually dealing with climate change is the almost universal assumption that it *has* to cost lots of money to fix. It’ll require investment, yes, but proper investment (in the normal business) sense means you get a return (profit) on that investment. Better energy efficiency means lower costs and higher profits. Given the rather low priority energy efficiency has been given since the 1970s oil shocks ended, I think there’s a lot of low hanging fruit out there.

Re #41 Hank, the current climate models are predicting the climate 50 and 100 years ahead e.g for 2100 CE. We will not know for sure that the predictions are correct until then. Weather models are different. They predict one or four days ahead, and these are always being checked, and improved. There is no feedback from the climate models so we just have to trust that they are OK.

We can also check to see if they can reproduce past climates, although that is no guarantee that they can successfully predict the future. For instance, they may be able to predict the current linear climate successfully, but fail to predict a future non-linearity.

This may seem rather philosophical, but you have to bear in mind that although the models can show the cooler glacial climate of the last glacial maximum, that is doene by tuning the CO2 sensitivity. Worse, the models cannot replicate the non-linear abrupt climate changes such as that at the end of the Younger Dryas stadial.

We have a peer review system where climate model experts check the papers of other climate modellers. If all the modelers are wrong, there is no independent way of discovering it.

You cite Santer as an example of someone who has checked that the models are correct, but that is not what he did. He argued that the models were correct hence the measurements made by the radiosondes must be wrong.

The NRC report about that says:

“Although the majority of observational data sets show more warming at the surface than in the troposphere, some observational data sets show the opposite behaviour. Almost all model simulations show more warming in the troposphere than at the surface. This difference between models and observations may arise from errors that are common to all models, from errors in the observational data sets, or from a combination of these factors. The second explanation is favored, but the issue is still open.”

If the first explanation is correct then no matter how many versions or parameters are varied, averaging will not improve the results!

Chris Rijk, I think that you are being a bit hard. It is a bit like insurance and if you have the job of persuading people to do something different which costs money then that is a fair analogy.

You are correct though, you will not learn anything new : that is not the point of the journal’s survey.

I have read the leader which is positive and more than I expected. I shall read the supplement over a few beers tomorrow.

If Gar Lipow is there I shall be pleased to hear what you have to say and of course Lynn, Grant (a bit tough in your latest comment above, statisticians are not supposed to be like that), and all of you regular and not so regular contributors. The Group’s response would be of interest for me of course and always.

We have a serious problem with warming which needs to be fixed and nobody wants to do anything about it : The Economist leader helps rather than hinders the pressure for action.

Grant (a bit tough in your latest comment above, statisticians are not supposed to be like that)

Thanks for giving me a good laugh at my own expense! It’s good that you can poke a few holes in my zealous statements in the gentlest possible way. Political zeal is better reserved for political blogs rather than scientific ones.